The aorta artery in the abdomen carries blood from the heart to the abdominal region. One disorder of the abdominal aorta is known as an abdominal aortic aneurysm, which is a permanent localized dilation of the arterial wall of the abdominal aorta. When dilation of the arterial wall is greater than 1.5 times the typical, i.e. nominal, diameter, it is referred to as an aneurysm. A normal abdominal aorta is shown in FIG. 1-1 (see U.S. Pat. No. 6,905,468). FIG. 1-2 shows a typical aortic aneurysm at. An aortic aneurysm is usually located below the renal arteries and the kidney arteries and above the aorta-iliac bifurcation. Below the aortic-iliac bifurcation are additional arteries. Abdominal aortic aneurysms are a fairly common disorder, occurring in approximately 5-7% of the population over age 60. Since effective screening programs are not yet established, the diagnosis of AAA is frequently made at the time of rupture or impending rupture, which leads to a dramatic increase of post-operative morbidity. (Daly, et al., 2004)
Abdominal aortic aneurysms, depending upon their size, result in pressure on adjacent tissue structure and organs, causing potential embolization and/or thrombosis in those tissues/organs. Rupture of the aneurysm typically results in death, and comprises approximately 2% of all deaths in men over 60 years of age.
Accurate diagnosis of an abdominal aortic aneurysm is important in preventing rupture, as well as in controlling the expansion of the aneurysm. Conventional two-dimension B-mode ultrasound scan devices are currently used to produce measurements of aortic aneurysms, both axially (longitudinally) along the aorta and laterally (radially) across the aorta. Typically, the accuracy is within three millimeters of the actual size of the aneurysm, using conventional CT or MRI processing. These conventional systems, however, are very expensive, both to purchase/lease and to maintain. Further, a trained sonographer is necessary to interpret the results of the scans. As a result, many aneurysms go undetected and/or are not consistently monitored after discovery, until rupture resulting in death of the patient.
A recent prospective study by Vidakovic, et al. (2006) sought to evaluate the diagnostic potential and accuracy in Abdominal Aortic Aneurysm (AAA) screening using an automatic bladder volume indicator (BVI) instrument. The BVI was originally designed for the estimation of post-void residual volumes. The device is inexpensive and can effectively be used after a short training. A measurement method of bladder volume is different between BVI and US, however several reports have found that BVI is as reliable as US to measure post-void residual urine. (Yucel, et al., 2005; Byun, et al., 2003)
In the Vidakovic et al. study AAA volumes were measured in 94 patients, and compared with 2D ultrasound and CT measurement to see if these comparisons can provide a method of screening AAA within certain volume thresholds. The reported results indicated there was an 89% agreement of the diameter measurements by ultrasound (US) as compared with those made with the bladder volume indicator (BVI). Using a cut-off value for the presence of AAA of 50 ml by BVI, the BVI technique predicted AAA with a sensitivity of 94%, a specificity of 82%, a positive predictive value of 88%, and a negative predictive value of 92%. The agreement between standard US and BVI in detecting an AAA was 89%.
This study showed the potential of using the BVI volume. Compared to other portable US devices used to screen patients, the BVI is simpler for use, requires a shorter training period, and is significantly cheaper. One barrier to its adoption is that the current device does not provide automatic conversion values and/or accurate values of AAA diameter. Moreover certain impediments exist to accurate readings of the region of interest that must be overcome for accurate predictive measurements.
Hence, it would be useful to a primary care physician or emergency personnel to have a low-cost device which provides accurate information concerning aortic aneurysms by providing AAA diameter measurements, without the necessity of a trained technician to interpret the scan results. Specifically, the art fails to provide a low cost system, method, and apparatus to automatically and accurately obtain and utilize data derived from an automatic bladder volume instrument (BVI) to provide values of abdominal aortic aneurysm (AAA) diameters.